The efficient activation of methane and the simultaneous water dissociation are crucial in many catalytic reactions on oxide-supported transition metal catalysts. On very low-loaded Ni/CeO₂ surfaces, methane easily fully decomposes, CH₄ → C + 4H, and water dissociates, H₂O→ OH + H. However, in important reactions such as the direct oxidation of methane to methanol (MTM), where complex interplay exists between reactants (CH₄, O₂), it is desirable to avoid the complete dehydrogenation of methane to carbon. Remarkably, the barrier for the activation of C–H bonds in CH_x (x = 1–3) species on Ni/CeO₂ surfaces can be manipulated by adding Cu, forming bimetallic NiCu clusters, whereas the ease for cleavage of O–H bonds in water is not affected by ensemble effects, as obtained from density functional theory-based calculations. CH₄ activation occurs only on Ni sites, and H₂O activation occurs on both Ni and Cu sites. The MTM reaction pathway for the example of the Ni₃Cu₁/CeO₂ model catalyst predicts a higher selectivity and a lower activation barrier for methanol production, compared with that for Ni₄/CeO₂. These findings point toward a possible strategy to design active and stable catalysts which can be employed for methane activation and conversions.

中文翻译：

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调节甲烷直接转化为甲醇的选择性：NiCu/CeO2 催化剂上 C-H 和 O-H 键裂解的双金属协同效应

在氧化物负载的过渡金属催化剂上的许多催化反应中，甲烷的有效活化和水的同时解离是至关重要的。在非常低负载的 Ni/CeO ₂表面上，甲烷很容易完全分解，CH ₄ → C + 4H，水分解，H ₂ O → OH + H。然而，在甲烷直接氧化成甲醇等重要反应中（ MTM），其中反应物（CH ₄，O ₂ ）之间存在复杂的相互作用，希望避免甲烷完全脱氢成碳。_{值得注意的是，Ni/CeO 2上 CH x} ( x = 1-3) 物种中 C-H 键的活化势垒表面可以通过添加 Cu 来控制，形成双金属 NiCu 簇，而水中 O-H 键的断裂容易度不受集合效应的影响，这可以从基于密度泛函理论的计算中获得。CH ₄活化仅发生在Ni 位点上，而H ₂ O 活化发生在Ni 和Cu 位点上。_{Ni 3} Cu ₁ /CeO ₂模型催化剂示例的 MTM 反应路径预测，与 Ni ₄ /CeO ₂相比，甲醇生产的选择性更高，活化势垒更低。这些发现指出了一种可能的策略来设计可用于甲烷活化和转化的活性和稳定的催化剂。